Method and device for an automatic supply of low molecular raw material for continuous production and spinning of polyamides



May 13, 1952 MORAVEC 2,596,272

METHOD AND DEvIcE FOR AN AuToMATIc SUPPLY OF LOW-MOLECULAR RAW MATERIAL FOR CONTINUOUS PRODUCTION AND SPINNING OF POLYAMIDES Filed March 19, 1948 Q BY %ZZMJ ATTORNEY Fatented May 13, 1952 METHOD AND DEVICE FOR AN AUTOMATIC SUPPLY OF LOW MOLECULAR RAW MA- TERIAL FOR CONTINUOUS PRODUCTION AND SPINNING OF POLYAMIDES Jan Moravec, Zlin, Czechoslovakia, assignor to Bata, narodni podnik, Zlin, Czechoslovakia Application March 19, 1948, Serial No. 15,754 In Czechoslovakia March 27, 1947 7 Claims.

1 There are known devices for a continuous production of polyamide fibres and threads where the raw material is continuously supplied to the melting space. The principal requirements of this method are an absolutely regular supply of the raw material and a perfect prevention of of access of air.

The present invention relates to a method and a device for an automatic continuous supply of the raw material in a polymerisation or polycondensation and spinning device. The supply is effected in such a way that in the melting space there is present a volatile solvent the vapours of which condense on the surface of the raw material, in an adjoining supply chamber. The condensed liquid dissolves the raw material and flows down into the melting space where it evaporates immediately and the cycle of events is continuously repeated. The regulation of th level is effected by means of a tube, connecting the supply chamber of the raw material with the melting space and elongated downwards in the form of a funnel. As soon as the level of the raw material rises because of excessive supply to the mouth of the tube or funnel, the mouth is closed, preventing thus further passage into the tube of the solvent vapours. Then these vapours can rise into an adjoining refiux cooler only, which is continuously open and the diameter of which at its narrowed parts is such as to allow the condensed solvent to act as a liquid seal, preventing access of air. As raw material hexamethylen-diammoniumadipate or G-caprolactam is a suitable example; as a volatile solvent methanol or low molecular chlorinated aliphatic hydrocarbons is or are most suitable.

The supply of the raw material is absolutely automatic, the level being maintained at such a height as to allow, by means of the tube, connected with the supply chamber of the raw material, only such a quantity of vapours as will be suflicient to dissolve an amount of raw material corresponding to the melted mass discharged by spinning.

An embodiment of the device according to the invention is diagrammatically illustrated on the accompanying drawing.

A polymerisation kettle l is heated from outside by electric current or in any other way, a heater IA being conventionally shown. The kettle I is filled to a predetermined level with e. g. fi-caprolactam polymerising therein and being pressed at the bottom by means of a suitable pump 2 through a filter 3 into a spinning nozzle 4, provided by a series of openings. The upper part of the kettle is (with exception of the thermometer not shown) provided by a reflux cooler 5 and by a tube 6, connected with the 2 inside space of a supply chamber 1, containing a pure G-caprolactam in pieces, mixed eventually with a suitable catalyst, fillers, stabilisers, plasticizers, antioxidating substances, means for de lustring or the like. The kettle I is of such dimensions as to allow the spinning mass in the kettle to attain, with respect to the given diameter of the spinning openings and the given spinning speed; the required degree of Viscosity or of molecular weight respectively. The vapours of methanol fill up entirely the space above the melting mass, the refiux cooler and the supply chamber. The supply chamber is tightly closed against any access of air and may be, if required,

connected with a balance-chamber, filled up by an inert gas, through an automatic valve which begins to act when the pressure within the supply chamber sinks due to the tube 6 having been closed for a rather long period of time, by cooling to such a degree as to produce the danger of letting the melted mass into the tube ii oy suction and that of its freezing in by polymerisation. If however the tube 6 is sufficiently wide, the entry of a substantial quantity of the melted mass into the tube 6 is impossible.

The filling of the supply chamber too may be automatic, the access of air being prevented by means of a device of a kind similar to that used for charging furnaces.

It will be manifest that the apparatus shown and hereinbefore described comprises in combination with the closed polymersation vessel I which contains as a molten mass a mixture of a monomeric or low-moleoular-weight polymerisable material, which is solid in the monomeric or low-molecular form but soluble in a volatile sol vent, and a volatile solvent thereof and which has the melt spinning assembly 2, 3 and 4 for continuously spinning the polymer into fibre filaments, the additional closed container 1 having a supply of the low-molecular-material in solid form, a conduit 5 between the container 1 and the vessel I for automatically regulating the supply of such material to the vessel, the conduit 6 having a mouth substantially below the upper limit of the vessel (so as to leave a space for the volatilised solvent) and at a level in the vessel near the surface level normal to the molten mass'therein, and means for heating the vessel so that internally it is hot. enough to maintain polymerisation of the low molecular material therein and also to vaporise the solvent therein so that the solvent vapor will rise through the conduit 6 to dissolve the solid material in the comparatively cool container I and the solution thus formed will flow through the conduit to close and open the mouth of the conduit to the admission of the solvent vapor. The combination also includes the reflux condenser convessel by having the monomeric or-low molecular polymerisable material together with a volatile solvent thereof as a molten mass within the polymerisation vessel I, also having a supply of said material in a solid state within the container 1, heating the contents of the vessel to maintain the polymerisation action and to vaporize the solvent, leading the solvent in a vaporous state to the container Ito condense therein and dissolve the solid material therein, leading the solution of said material in the solvent to flow into the vessel for polymerisation therein of such material, and utilising the rising and falling surface of the molten mass in the vessel to close and open the flow thereinto of the dissolved material. Moreover, vapor due to excessive vaporisation of the volatile solvent in the molten mass is led from the polymerisation vessel, condensed to liquid form and led, to flow back into the vessel.

Having now particularly described and ascertained the nature of my said invention and in what manner the same is to be performed, I declare that what I claim is:

1. In the continuous production of fibre filaments composed of a synthetic polyamide, which has to be delivered in a molten state from a polymerisation ve-sselfor extrusion by a spinning assembly, a method of automatically regulating the supply'of a polyamide-forming monomeric raw material which is solid at normal temperature to the polymerisation vessel, which method consists in placing said raw material together with a volatile solvent thereof as a hot molten mass within a polymerisation vessel, also placing a supply of said raw material in a solid state within a container, heating the contents of said vessel to maintain the polymerisation action and to vaporise the solvent, passing the solvent in a vaporous state through a conduit to said container to condense therein and dissolve the solid raw material therein, leading the solution of said material in the solvent to flow through said conduit into said vessel for polymerisation therein of said material, closing and opening said conduit by the rising and falling surface of the molten mass in said vessel to stop and start the passage of the vaporous solvent to said container so as to regulate the dissolution of the solid material and therefore the rate of supply of the dissolved material to the polymerisation vessel, removing any excess vapor trapped in said vessel above said surface, and continuously delivering the molten polyamide from said vessel and extruding said polyamide.

2. The method according to claim 1 in which vapor due to excessive vaporisation of the volatile solvent in the molten mass is led from the polymerisation vessel, condensed to liquid form and led to flow back into said vessel.

3. The method according to claim 1 in which the volatile solvent is methanol.

4. In the continuous production of fibre filaments composed of a synthetic polyamide which has to be delivered in a molten state from a poly- 4 merisation vessel for extrusion by a spinning assembly, a method of supplying a polyamide-forming monomeric raw material at a regulated rate to the polymerisation vessel, which method consists in heating a mass of the raw material to maintain it molten, supplying a volatile solvent in a liquid condition to said mass to vaporise the solvent, passing the solvent in a vaporous state out through a conduit to a supply of the raw material in a solid state in order to condense on the solid raw material and dissolv it progressively, leading the dissolved raw material in through said conduit to said molten mass to maintain the quantity thereof, closing said conduit periodically by the molten mass to automatically stop the passing of the solvent vapor to the solid raw material in order to regulate the rate of supply thereof to the polymerisation ves- V sel, removing any excess vapor trapped in said vessel above said molten mass, and continuously delivering the molten polyamide from said vessel and extruding said polyamide.

5. The method according to claim 4 which consists also in condensing vapor due to excessive and which has a spinning assembly for continu-' ously withdrawing from said vessel the molten polyamide and spinning it into fiber filaments, an additional comparatively cool closed container adapted to contain a supply of the raw material in solid form, a conduit between said container and vessel for automatically regulating the supply of said material to said vessel, said conduit having a mouth substantially below the upper limit of said vessel and at a level in said vessel near the surface level predetermined for the molten mass to be contained therein, and means for heating said vessel to maintain polymerisation of the raw material therein and also to vaporise the solvent therein so that the solvent vapor will rise through said conduit to dissolve the solid material in said container and the solution thus formed will flow through said conduit to replenish the molten mass, the surface of which serves to close and open said mouth to the admission of the solvent vapor.

'7. The combination according to claim 6 including also a reflux condenser connected at a level above said conduit mouth to said polymerisation vessel and adapted to receive solvent vapor produced to excess in said vessel and to condense said vapor and return the liquid condensate to said vessel.

JAN MORAVEC.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name a Date 2,071,250 Carothers Feb. 16, 1937 2,273,188 Graves Feb. 17, 1942 2,278,875 Graves Apr. 7, 1942 2,289,774 Graves July 14, 1942 2,295,942 Fields Sept. 15, 1942 2,369,506 Weibel Feb. 13, 1945 2,486,410 Howatt Nov. 1, 1949 

6. IN COMBINATION WITH A CLOSED POLYMERISATION VESSEL WHICH IS ADAPTED TO CONTAIN AS A MOLTEN MASS A MIXTURE OF A POLYAMIDE FORMING MONOMERIC RAW MATERIAL AND A VOLATILE SOLVENT THEREOF AND WHICH HAS A SPINNING ASSEMBLY FOR CONTINUOUSLY WITHDRAWING FROM SAID VESSEL THE MOLTEN POLYAMIDE AND SPINNING IT INTO FIBER FILAMENTS, AN ADDITIONAL COMPARATIVELY COOL CLOSED CONTAINER ADAPTED TO CONTAIN A SUPPLY OF THE RAW MATERIAL IN SOLID FORM, A CONDUIT BETWEEN SAID CONTAINER AND VESSEL FOR AUTOMATICALLY REGULATING THE SUPPLY OF SAID MATERIAL TO SAID VESSEL, SAID CONDUIT HAVING A MOUTH SUBSTANTIALLY BELOW THE UPPER LIMIT OF SAID VESSEL AND AT A LEVEL IN SAID VESSEL NEAR THE SURFACE LEVEL PREDETERMINED FOR THE MOLTEN MASS TO BE CONTAINED THEREIN, AND MEANS FOR HEATING SAID VESSEL TO MAINTAIN POLYMERISATION OF THE RAW MATERIAL THEREIN AND ALSO TO 